The frame rate is the rate at which the infrared detector creates images. For a 9 Hz camera it does so 9 times per second, and for a 60 Hz camera 60 times per seconds. If the LCD/viewfinder has a higher display rate, the infrared image will just get repeated a number of times.

All cameras of the same kind have the same infrared properties, irrespective of the frame rate. The thermal time constant is a measure of how quickly the infrared detector itself reacts to fast changes in the incoming radiation. It is completely unrelated to the frame rate.